A Wet Dry is a wonderful way to house/develop bacteria that converts ammonia into nitrite and nitrite into nitrate... but will do absolutely nothing for nitrate removal...
A refugium will remove ammonia, nitrite as well as nitrate...
Since the refugium takes filtration one step further, I feel it should be regarded as a superior form of filtration. Thus I completely disagree with the conclusive opinion shared above... Though I am interested to hear the reasoning behind the opinion...